In recent years, optical coherence tomography (OCT) has established itself as routine modality for diagnosing retinal disorders. Because of its 2D slice data records or 3D data records of the retina, it complements the previous conventional fundus recordings such as color recordings and fluorescence angiography recordings and also the more recent autofluorescence recording measurements and macula pigment measurements by the fundus cameras. In so doing, fundus camera recordings and OCT measurements were previously, for reasons of instrument complexity, made in different instruments. The procedures were designed accordingly, particularly in the large clinics as well. It is only in the last few years that combination instruments have also been commercially available, which are able to make both fundus camera recordings and OCT measurements.
Such combination instruments are advantageous in that, as a result of the reduction from two instruments to one, less space is required than in the case of two separate instruments. Furthermore, reseating of the patient is avoided if recordings or measurements of different modalities should be made for one and the same patient, which has a positive influence on the procedures in the medical practices and clinics. However, the existing combination instruments have a number of deficiencies.
In the existing combination instruments, fundus camera recordings and OCT measurements occur simultaneously or shortly one after the other, as described in US 2007/159595, and the signals of the modalities are separated by a dichroic mirror, as likewise described in US 2007/159595 or as already described in U.S. Pat. No. 5,537,162. If fundus images and OCT signals are recorded simultaneously, it is possible to register both modalities laterally to one another without movement artifacts, but the signal strength of both modalities is reduced compared to an individual measurement since, for safety reasons, the maximum illumination intensity permissible for the eye must be divided between both/several simultaneously recorded modalities. To the extent that the wavelengths to be separated are far apart, dichroic mirrors can be used with great efficiency. However, the increasing number of modalities and optical assistance functions, such as fixation, positioning and focusing aids, lead to the wavelength regions to be separated lying ever closer together, and so the separation efficiency of the dichroic mirrors reduces and hence the signal intensity of the individual modalities is also reduced. In the existing combination instruments, the assistance functions of a conventional fundus camera are furthermore inherited and employed in the same manner as is conventional for conventional fundus cameras. Aligning the camera on the eye in order to minimize reflections at the cornea takes place using positioning markers and the focusing on the retina takes place using focusing markers; both in the IR (infrared) live image from the fundus camera. The positioning/focusing settings for the other modalities are then coupled to the recording settings of the focused IR live image in the same fixed manner for all patients. In particular, the focus position of the OCT and of the fundus recording is fixedly coupled to the focus position of the focused IR live image. This rigid coupling leads to the focus setting not being optimal for every one of the modalities, such as color recordings or fluorescence angiography recordings, and/or not being optimal for each examination object in the retina, such as the nerve fiber layer or the pigment epithelium, and/or not being undertaken in an optimal manner for each patient. This non-optimal focusing then leads to fine lateral structures of the examination objects possibly no longer being sensed correctly.
Furthermore, the procedure of the measurements of the individual modalities in existing combination instruments is strongly oriented toward predefined application problems. By way of example, this is described in US 2012/121158. In accordance with US 2012/121158, different measurement procedures consisting of measurements from different modalities and the associated recording parameters thereof are predefined for different problems such as macula disorders or glaucoma disorders. Then, in order to measure a patient, one problem or measurement procedure is selected and the measurements defined in the measurement procedure are carried out. An advantage of this is that the measurement procedure ensures that all recordings required to diagnose a clinical picture are in fact also made.
However, this also has the following disadvantages: by way of example, if glaucoma is suspected and a measurement procedure which comprises the optic nerve papilla in an OCT measurement and in a fundus recording is started for the patient, it is subsequently possible to start a measurement procedure for examining a macula disorder using an OCT measurement and a fundus recording of the macula, but this is only expedient in the state of the eye dilated by drops since the first fundus recording would otherwise lead to pupil narrowing, making the measurement of the second measurement procedure impossible. With an increased flexibility in the measurement procedure, the same result could be obtained by an OCT macula, an OCT optic nerve papilla recording and a 50 degrees fundus recording, even for an eye not in the state dilated by drops. Although only one further set could be defined by precisely this alternative measurement procedure, the number of measurement procedures for covering the combinations occurring in practice very quickly becomes unclear. The invention is directed to a solution to the aforementioned problems, which easily and cost-effectively improves the recording quality of the individual modalities of a combination instrument made of fundus camera and OCT system and also ensures the flexibility of such a combination instrument, without increasing the operational complexity thereof.
The object is achieved by a device and method consisting of a fundus camera with an OCT measurement module, in which, after the focusing objective, a mirror switches the light to be detected either to the OCT measurement module or to an image detector.